This invention generally relates to load bearing members for use in elevator systems. More particularly, this invention relates to an elevator belt assembly having a specialized jacket and cord arrangement.
Elevator systems typically include a cab and counterweight that move within a hoistway to transport passengers or cargo to different landings within a building, for example. A load bearing member, such as roping or a belt typically moves over a set of sheaves and supports the load of the cab and counterweight. There are a variety of types of load bearing members used in elevator systems.
One type of load bearing member is a coated steel belt. Typical arrangements include a plurality of steel cords extending along the length of the belt assembly. A jacket is applied over the cords and forms an exterior of the belt assembly. Some jacket application processes result in grooves being formed in the jacket surface on at least one side of the belt assembly. Some processes also tend to cause distortions or irregularities in the position of the steel cords relative to the exterior of the jacket along the length of the belt.
FIG. 1, for example, illustrates both of these phenomena. As can be seen, the spacing between the exterior of the jacket 20 and the cords 22 varies along the length of the belt. As can be appreciated from the illustration, the cords 22 are set within the jacket as if they comprise a series of cord segments (i.e., 24, 26) of equal length corresponding to the spacing between the grooves 30. The illustration of FIG. 1 includes an exaggeration of the typical physical cord layout for purposes of illustration. The actual distortions or changes in the position of the cords relative to the jacket outer surfaces may not be discernable by the human eye in some examples.
When conventional jacket application processes are used, the manner in which the cords are supported during the jacket application process tends to result in such distortion in the geometry or configuration of the cords relative to the jacket outer surfaces along the length of the belt.
While such arrangements have proven useful, there is need for improvement. One particular difficulty associated with such belt assemblies is that as the belt moves in the elevator system, the grooves and the cord placement in the jacket interact with other system components such as the sheaves and generate undesirable noise, vibration or both. For example, as the belt assembly moves at a constant velocity, a steady state frequency of groove contact with the sheaves creates an annoying, audible tone. The repeated pattern of changes in the cord spacing from the jacket outer surfaces is believed to contribute to such noise generation.
An alternative arrangement is required to minimize or eliminate the occurrence of vibrations or an annoying tone during elevator system operation. This invention addresses that need.